to the delicate and potentially dangerous space walk, suddenly being planned by nasa this evening. Tonight, we've learned they're now readying astronauts for those walks, if mission control can't fix the urgent problem on the international space station. Here's abc's linzie janis tonight. Reporter: Nasa engineers in houston have been working around the clock since wednesday, trying to fix a malfunction in the international space station's cooling system remotely. But so far, no luck. What is actually going wrong with the loop? Reporter: Tonight, mission control saying it will make a decision next week on whether a series of dangerous space walks are needed to make the repair. Astronaut doug wheelock made the same fix in 2010 in his own space walk. When we open that hatch and send people outside, it is always dangerous. It's a dangerous environment. It's really inhospitable. When you go outside, you deal with a lot of things mechanically that can go wrong. Reporter: But this weekend, from 230 miles above the earth, american astronaut rick mastracchio says the team is ready. We have the spare parts. We have the training. We have the skills. And, of course, going out and doing a space walk is always very excited, yet very challenging. Reporter: This would be the first space walk since nasa suspended them in july after an italian astronaut nearly died when his space suit filled up with water. If nasa commissions this space walk, the first one could happen on thursday. On thursday. A lot of eyes on nasa this week. Linzie, thank you.

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